This invention relates to selectively controlled cooling of a workpiece and, more particularly, to the guiding of a cooling fluid to follow along a workpiece surface for the selective control of convective cooling coefficients between areas of a workpiece as a function of differences in surface areas or mass or both.
It is common practice, for example in the metallurgical art, to heat treat and then cool an article or workpiece for one or more of a variety of reasons. These include cooling to develop desired microstructure and mechanical properties while avoiding physical defects such as cracking, controlling distortion and controlling residual stresses which can impact such characteristics as machinability during manufacture or repair as well as article operating life.
A variety of methods and apparatus for cooling certain workpieces has been reported. However, these are directed or related to the cooling of generally solid workpieces or workpieces of relatively simple shape, or both. Some approaches include varying areas of cooling exterior surfaces of a workpiece, for example, as a function of workpiece thickness. Examples of such reports include U.S. Pat. No. 2,890,975 - Lenz (patented Jun. 16, 1959); U.S. Pat. No. 3,470,624 - Plotkowiak (patented Oct. 7, 1969); U.S. Pat. No. 4,610,435 - Pfau et al (patented Sep. 9, 1986); and U.S. Pat. No. 4,653,732 - Wunning et al (patented Mar. 31, 1987). In other reports, internal and external surfaces of an article, such as a vehicle wheel, are cooled by jets of cooling fluid sequentially directed separately first toward an inside surface and then toward an outside surface, as in U.S. Pat. No. 4,767,473 - Berg (patented Aug. 30, 1988). More particularly in connection with turbomachinery components, such as a simple shaped, single stage, solid rotor disk, jets of cooling fluid from selectively sized and positioned nozzles or orifices have been directed at the external surface of the relatively simple disk, such as in Invention Registration H777 -Natarajan, (published May 1, 1990), or separately at the external surface and at the bore of a simple, single stage disk, as in U.S. Pat. No. 4,769,092 - Peichl, et al (patented Sep. 6, 1988). The disclosures of each of the above reports are hereby incorporated herein by reference.
However, the controlled cooling of a complex sized and shaped workpiece which includes adjacent areas of high and low volume and/or high and low available convective surface area will generally have protrusions which will impede or block the flow of cooling fluid and requires a different cooling method and apparatus than has heretofore been reported. For example, such workpieces have been designed for use in the manufacture of at least a portion of an advanced, drum-like compressor and turbine of a gas turbine engine. These workpieces generally are a combination of articles of revolution with protruding shelves running perpendicular to the axis. Improvement in known methods and apparatus is needed to avoid undesirable cooling fluid velocities along the surface of complex shaped workpiece areas, for example, the recesses, channels, indentations or changes in inflection or shape of a complex workpiece as described above. Although the method and apparatus described herein is particularly suited for use on complex geometries, its use is not limited to such.